This article will help you read and understand your pathology report for extramammary Paget disease of the vulva.
by Emily Goebel, MD FRCPC, reviewed and updated on September 19, 2020
The vulva is the external part of the female genital tract. It forms the opening of the vagina and includes the mons pubis, labia majora, labia minora and clitoris. The vulva is composed of skin. The surface of the skin is called the epidermis and is mostly made up of squamous cells. The tissue beneath the epidermis is called the dermis, it contains blood vessels and connective tissue. Another name for the dermis in this part of the body is stroma.
Extramammary Paget disease is a cancer that develops in the epidermis of the vulva. It is considered a type adenocarcinoma. Paget disease rarely spreads to lymph nodes or other parts of the body. It can, however, re-grow (recur) in the same location after surgery.
This diagnosis is usually made after a small sample of tissue is removed in a procedure called a biopsy. The entire tumour will usually be removed fully in a larger surgical procedure called an excision or vulvectomy.
The cancer cells in extramammary Paget disease usually stay in the epidermis. Invasion is a word pathologists use to describe the spread of cancer cells from the epidermis into the dermis or stroma below.
Tumours with deep invasion into the dermis or stroma are more likely to spread to lymph nodes or other parts of the body.
Your pathologist may perform a test called immunohistochemistry to confirm the diagnosis and to exclude other cancers that may look similar to extramammary Paget disease.
The tumour cells will be positive or reactive for immunohistochemical markers such as CK7 and GCDFP-15 and negative or non-reactive for p63 and S100, which you may see included in your pathology report.
Tumour size is a measurement of the area with Paget disease. It is usually described in centimeters. Some reports will describe the tumour size as the extent of disease.
A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. A negative margin means that no cancer cells were seen at the cut edge of the tissue. In contrast, a positive margin means that cancer cells were seen at the cut edge of the tissue. A positive margin increases the risk that the tumour will grow back in that location.